Argon fluoride excimer laser source for sub-0.25 mm optical lithography

The spectral characteristics of an ELS-4000 excimer laser operating at 193 nm and employing two different line-narrowing schemes have been studied. Partial bandwidth reduction (72 pm FWHM) was achieved using a single dispersive prism. The laser generated an average output power of 4 W, making it a useful source of VUV radiation for broad-band 193 nm lithography. Narrow-band operation (5.5 pm FWHM) was attained using a prism-grating combination. The maximum narrow-band energy was 6 mJ; however, the average power was low (0.6 W). Improvements in the gain generator and optics will be needed to extract higher power levels for narrow-band lithographic applications.